Does ontogeny modulate irradiance-elicited plasticity of leaf traits in saplings of rain-forest tree species? A test with Dicorynia guianensis and Tachigali melinonii (Fabaceae, Caesalpinioideae)

Abstract

Keywords: plant architecture / phenotypic plasticity / photosynthetic capacity / leaf structure / tropical rain forest Abstract • Irradiance elicits a large plasticity in leaf traits, but little is known about the modulation of this plasticity by ontogeny. Interactive effects of relative irradiance and ontogeny were assessed on leaf traits for two tropical rainforest tree species: Dicorynia guianensis Amshoff and Tachigali melinonii (Harms) Barneby (Fabaceae, Caesalpinioideae).• Eleven morphological and physiological leaf traits, relative to photosynthetic performance, were measured on saplings at three different architectural development stages (ASD 1, 2 and 3) and used to derive composite traits like photosynthetic N-use efficiency. Measurements were made along a natural irradiance gradient.• The effect of ASD was very visible and differed between the two species. For Dicorynia guianensis, only leaf mass-per-area (LMA) significantly increased with ASDs whereas for Tachigali melinonii, almost all traits were affected by ASD: LMA, leaf N content and photosynthetic capacity increased from ASD 1 to ASD 3. Photosynthetic N-use-efficiency was not affected by ASD in any species.• Leaf traits were severely modulated by irradiance, whereas the degree of plasticity was very similar among ASDs. Only few interactions were detected between irradiance and ASD, for leaf thickness, carbon content, and the ratio Chl/N in T. melinonii and for photosynthetic capacity in D. guianensis.• We conclude that ontogenic development and irradiance-elicited plasticity modulated leaf traits, with almost no interaction, i.e., the degree of irradiance-elicited plasticity was stable across development stages and independent of ontogeny in these two species, at least in the early stages of development assessed here. Mots-clés :architecture des arbres / plasticité phénotypique / capacité photosynthétique / structure des feuilles / forêt tropicale humide Résumé -L'ontogenèse module-t-elle la plasticité des traits foliaires induite par la lumière dans des semis d'arbres de forêt tropicale humide ? Un test avec Dicorynia guianensis et Tachigali melinonii (Fabaceae, Caesalpinioideae).• Les traits foliaires varient fortement avec l'éclairement mais également avec l'ontogenèse. Cependant, l'impact de l'ontogenèse sur la plasticité induite par l'éclairement reste mal connu. Les interactions entre ontogenèse et éclairement relatif ont ainsi été étudiées pour des traits fonctionnels foliaires de deux espèces de forêt tropicale humide de Guyane française : Dicorynia guianensis Amshoff et Tachigali melinonii (Harms) Barneby (Fabaceae, Caesalpinioideae). • L'impact de stades successifs de développement différait entre espèces. Pour D. guianensis, seule la masse surfacique (LMA) a augmenté significativement avec les stades de développement tandis que pour T. melinonii, presque tous les traits foliaires étaient modulés. Pour cette espèce, LMA, teneur en N et capacité photosynthétique ont augmenté de ASD 1 à ASD 3. Par contre, l'efficience d'utilisation de N ...

Growth-unit structure in trees: effects of branch category and position on Nothofagus nervosa, N. obliqua and their hybrids (Nothofagaceae)

“…All individuals chosen for this study had relatively unshaded upper branches and shaded lower branches, so that had light conditions ruled GU traits, within-individual variability in these traits would have been higher than it actually was. Thus, the results sustain the idea that microclimate modulates the variations in GU traits around mean values typical of each ontogenetic stage within the species' sequence, in compliance with previous studies (Suzuki 2003;Suzuki and Suzuki 2009;Fernández et al 2007;Chaubert-Pereira et al 2009;Coste et al 2009). Thomas and Winner (2002), Ishida et al (2005), Holdaway et al (2008 and Valladares and Niinemets (2008) underlined the relevance of axis differentiation for the acclimation of plants to contrasting conditions.…”

Seasonal leaf dynamics for tropical evergreen forests in a process-based global ecosystem model

“…The relationship between V c,max and leaf age ( Fig. 1) is supported by different studies (Ackerly and Bazzaz, 1995;Coste et al, 2009;Kitajima et al, 1997;Kitajima et al, 2002) that showed a decreasing photosynthetic capacity with leaf age for tropical species. Furthermore, the relation is supported by the findings of Steppe et al (2011) and Chapin et al (2002) that reported on decreasing photosynthetic capacity with leaf age due to modifications in leaf size, thickness, density, foliar nitrogen content and lignin content in species worldwide.…”

Long-term physiological and morphological acclimation by the evergreen shrub Buxus sempervirens L. to understory and canopy gap light intensities

“…Plants that grow in full sun reduce investment in nitrogen for leaf chlorophyll, but increase the production of pigments involved in photoprotection, including xanthophylls (Bilger and Bjorkman 1990;Demmig-Adams 1990;Galmés et al 2007;Matsubara et al 2009). Under long-term exposure to high irradiance, carbon allocation is directed towards high leaf dry mass per unit area (LMA; Lusk et al 2008;Poorter et al 2009;Coste et al 2010), dense branching and leaf clumping (Ali and Kikuzawa 2005). Leaf inclination also tends to increase, resulting in lower radiation interception per unit leaf area when solar zenith angles are small (Falster and Westoby 2003).…”